When I open my project all shadows have gone
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In addition to Christopher Bennet's comment (making sure you are in the rendered viewport, Z -&gt; Rendered) I will suggest another possible cause for future readers.
In Eevee, one can turn off shadows manually for each light source. You can click on a light source in the outliner, go to object data properties (the light bulb). There you can select two checkboxes: Shadow and Contact shadows. Check if these have not been accidentally turned off.